Answer this question truthfully
### Question: What causes Obstructive uropathy?
### Response: Obstructive uropathy occurs when urine cannot drain through a ureter (a tube that carries urine from the kidneys to the bladder). Urine backs up into the kidney and causes it to become swollen (hydronephrosis).
Obstructive uropathy is grouped according to whether it affects one or both kidneys and whether it occurs suddenly or is long-term:
Chronic unilateral obstructive uropathy - Long-term uropathy that affects one kidney Chronic bilateral obstructive uropathy - Long-term uropathy that affects both kidneys Acute unilateral obstructive uropathy - Sudden uropathy that affects one kidney Acute bilateral obstructive uropathy - Sudden uropathy that affects both kidneys
Common causes of obstructive uropathy include the following:
Urinary tract stones Ureteral stones Bladder stones Urinary tract tumors Retroperitoneal fibrosis Benign prostatic hyperplasia (enlarged prostate) Tumors of nearby organs Bladder or ureteral cancer Colon cancer Cervical cancer Uterine cancer Any cancer that spreads Idiopathic hydronephrosis of pregnancy